Need help clearing p0303

Have you tried cleaning the EGR ports within the intake manifold? What about the EGR cooler?

 

When you say swapped coils and injectors does that mean you replaced them? If not I would for cylinder 3. A weak hv battery will cause chatter on initial acceleration especially when the hv charge indicator is low. Could be two problems.

 

welcome!
have you checked the service manual?

 

That is not enough compression. The min spec is here.

Standard compression pressure:
1373 kPa (14.0 kgf/cm2, 199 psi) or more Minimum pressure:
1079 kPa (11.0 kgf/cm2, 157 psi)
Pressure difference between each cylinder:

Sounds like the ICE is worn out.

 

I suggest a compression test and a leakdown test.

I don't think your compression test was done properly. 65-70 psi is very low and would cause misfires on the other cylinders as well. @cnc97 listed the values you should be seeing for this engine and I highly doubt that a 60k mile engine is worn out.

I am curious if the misfires start right away but take a few minutes to really become severe. Do you have access to a scan tool with a decent set of live data pid's? A lot of things can change during engine warm up - injector duty cycles change, cam timing changes, engines can/will go into closed loop, egr behavior changes, etc. As a general starting point you need to find a way to record data from the relevant pid's and find out what exactly is happening when the misfires start (or become more severe).

 

Many of the most baffling problems are the result of assumptions that incorrectly validated a component when it was actually bad or intermittent. You go through the whole process and check off the boxes only to find one of those things that was “checked” was at fault in the end. I have seen P0303s that were actually multiple coils. Hopefully you have checked the misfire counters and have cleared all codes and looked for the newest indication.

What pro mechanics often do is put a scope on the coil and injector signals. The characteristic waveforms may be distorted or missing on a bad circuit. Often, with experience, they can spot head gasket and timing problems at the same time. Certainly the ecu drives those circuits but is obvoiusly the last item to be replaced, in part because of the setup required.

I would lean against an egr problem since you have inspected it recently. Plus it throws its own codes as do most sensors. Sometimes it pays to have a pro check it with their advanced tools.

 

If the compression tester was accurate, then compression is leaking past the valves back into the intake and exhaust. I’d try a second test. Techstream will do the test, or you can run it how I did mine. Remove all the plugs and coils, unplug the injectors. Install the gauge unit the first cylinder. Put it in ready mode and hit the gas. The engine spinup will get the job done.

Try that and report results back here.

 

I will remind you that a weak hv battery will cause chatter on initial acceleration especially when the hv charge indicator is low. See if it goes away from a dead stop with the hv battery showing a full charge. The engine is tuned to require a certain amount of help from the hv battery which goes away if the unit is approaching failure. Mpg usually goes down as well.

 

I had not thought of that. And you even said that in your earlier post.

Or, if the engine swap was recent, the damper or clutch plate could have vibrated loose. The chatter of the plate or flywheel could be interpreted as spark knock. The removal of ignition timing by the ICE ecm could cause a misfire when that happens.

 

That’s better compression readings. Try adding a couple of tablespoons of oil to #4. If it comes up then the rings are leaking down. Move an injector from #1to #3. See if the misfire follows the injector. You may find the injector simply wasn’t plugged in properly as well.

 

It sounds like he is in open loop on startup and then the car goes into closed loop then the misfire starts.
On startup the car starts in open loop and uses a default strategy until the temperature comes up and then goes into closed loop when it starts taking information from the O2 sensor or whatever Toyota calls it as well as other inputs.
I can't explain why it is #3 cylinder giving you the problem. Sometimes OBDII reports the wrong cylinder.

 

He said a found a bad coil, probably caused his p0303. Should change them all because the rest have the same history.

 

This does not sound like the part of a misfire after 60 seconds.

 

Could the coil could be heat sensitive. Opening when warm, closed and working when cold.